I've thought some more about this, and I now feel more strongly than I did before thinking it through.
I'm less comfortable than I was about settling for Magnetic North as one's habitual datum.
Firstly, because it means delegating to technology a job which I think is too important to habitually leave to "others": in this case, allowing for Variation.
One risk of doing so is that one day, we will assume it is being done, only to find -too late - that it has not.
(probably not because of a technology failure, but because circumstances have changed: we're on someone else's boat, or we're relying on unfamiliar aids in an emergency
, or whatever).
It's a bit like relying on your remote
to lock your car, instead of doing it manually.
All it takes is one loose connection for one door to remain unlocked.
If you have to check all the doors yourself, the technology is not providing any added value: you might just as well lock them yourself.
OK, a car is only a car, so it's a tradeoff we are all happy to make.
But a navigational error is not just possibly going to lose us a boat, it might lose us our life, or worse.
I'm pretty sure I'd be checking the doors were all locked the old fashioned way, if a homicidal maniac was circling the car.
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Secondly because adopting a Magnetic mindset means we're swimming metaphorically in an isolated pool, in terms of how we handle geographical information.
It has been pointed out that it makes it harder to use information from the past (sailing directions, pilots, cruising guides
, historical accounts etc)
but it also makes any notes we take risky for the future - particularly in places where variation changes quite quickly, and sailors live quite long.
That is, unless we note against each bearing we record
, not only the fact that it was magnetic, but the year when we measured it, or better still, the variation at that time.
Idea: why not note it down in degrees True?
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Thirdly, I think it's a good idea to train one's sense of 'situational awareness' over one's lifetime by developing the habit of regularly taking notice of things like:
- the direction of the sun when it reaches the highest point it its daily arc
(not just at sea, but from familiar locations on land) which is obviously true North
- the direction of the sun rising and setting at the equinox, which almost as obviously is true East and true West
- the way that latter direction changes during the year, as a function of latitude, some aspects of which are quite counterintuitive
Having such habits means we can easily use the sun as a crude compass, and this can be a major help when cut adrift from technological direction-finding aids, on land or at sea.
technological aids, the sun can occasionally be useful: I used it recently when I was lent a hand-held GPS for a land-based mission of resupplying tracking tunnels for pest species.
It was new to the person lending it to me, so they had mis-described how to use the direction-finding capabilities; the method they told me was applicable to the previous model, but once I was on task it was giving meaningless behaviour with this unit.
For those muttering "RtFM", there was no "M" to "FR", and neither cellphone nor coverage.
I was able to instead refer to the approximate bearing to the next waypoint, given as (say) "NW", and (not having a compass) use the sun to tell me roughly where that was.
Given that I knew the exact distance to the waypoint, knowing the rough direction saved me
from having to traverse a lot of extra distance, sometimes through rather impenetrable and even hostile ground cover. Probably saved nearly a day, and lots of scratches and nettle stings.
It seems to me that such a 'situation awareness' mindset needs to be based on having True North as the dominant reference, and Magnetic in a subsidiary role.